Anticoerosive



Patented Mar. 13, 1945 ANTICOBBOSIVE Emmett R. Barnum, Berkeley, andErnest W. Zublin, Sausalito, Callf., assignors to Shell DevelopmentCompany, San Francisco, Calif., a corporation of Delaware No Drawing.Application February 8, 1943, Serial No. 475,201

24 Claims.

The present invention relates to compositions having anti-corrosive, andespecially rust-protective, properties, and more particularly deals withcompositions comprising a substantially neutral vehicle, such asnormally liquid or nor= mally solid hydrocarbons, alcohols, esters (e.g., fatty oils and natural waxes) water, etc., containing finelydispersed small amounts of certain free dicarboxylic acids.

Metallic surfaces, particularly those containing iron, requireprotection'against the hazard of corrosion in the presence of water.Moisture readily attacks finished or semi-finished metal objects unlessthe metal surface is covered during storage or shipment by a protectivecoating such as a slushing oil; water in Diesel engine fuels oftencorrodesclosely fitted parts such as are found in Diesel engine unittype injectors; waterin turbines corrodes turbine lubricant circulatorysystems, particularly the governor mechanisms of steam turbines; andwater in hydrocarbon oils such as gasoline rusts steel storage tanks anddrums; water in anti-freeze compositions causes corrosion in automobileradiators, etc. Corrosion not only has a deleterious efiect upon themetal surfaces, but also frequently loosens finel divided metal oxideswhich may act as oxidation catalysts increasing the rate ofdeterioration of various organic compounds with which they come incontact or may enter between moving parts of machinery where they act asabraslves.

It is a purpose of this invention to produce potent corrosion-protectivecompositions of wide applicability. Another purpose is to produceslushing compositions of improved corrosion-protective properties. Aspecific purpose is to produce rust-protective hydrocarbon compositions,i. e., including various Diesel oils, steam turbine oils, greases, etc.Still another purpose is to provide anti-freeze compositions free from atendency to cause rusting. Further, it is a purpose to produce anon-oily composition which can be used for rust-protection of ferrousmetal and in general for protecting various metals against corrosion.

We have discovered that dicarboxylic acids having at least 16 carbonatoms in which there is an ether type radical of an element selectedfrom the group consisting of oxygen, sulfur, selenium and telluriumclose to at least one and preferably both carboxyl radicals, whichradical branches from the carbon chain linking .the car- To illustrate:

looxyl radicals, are such potent corrosion inhibitors that they arecapable of effectively preventing rusting of ferrous metals affordingpmtection not only against pure water, but against etc.

The general formula of our acids may be represented as follows:

coon

((RX'(CH1)I)) 0-0 u OOH wherein u is an integer from 1 up to about 8 andpreferably 2, v is an integer from zero up to about 8, preferably zero,w is at least 1, preferably 1 or 2,v

and never greater than u, X is an element of the class 0, S, Se or Te,and R is a hydrocarbon rad-' ical. Unoccupied valences may be tied tothe same or different hydrogen or hydrocarbon radicals.

The several hydrocarbon radicals may be allphatic, alicyclic, aromaticor mixed and may contain substituents which are preferably not toostrongly polar, such as halogen, but are preferably free from highlypolar substituents, such as hydroxyl, carboxyl, carbonyl, amino,hydrosulfide, etc. For maximum stability against deterioration byoxidation, the acid should contain not more than one aliphatic doublebond per hydrocarbon radical, and preferably none.

As indicated above, the acid should contain not less than 16, andpreferably at least 20 and up to 60, carbon atoms for goodanti-corrosion properties. Also, the closeness of the 0, S, Se or Te, asthe case may be, to the carboxyl radicals has a bearing on thisproperty, in general the closer they are, the greater the protectivepower. Because of this, homologues in which the ether linkage is inalpha or beta position to at least one and preferably both carboxylradicals are most desirable.

The simplest of these acids are the malonic acid derivatives illustratedbelow:

wherein again X is O, S, Se or Te and R is a hydrocarbon radical.However, this type of acid is thermally quite unstable, easily losingCO1. Therefore, for many purposes it is not desirable. succinic orfumaric (maleic) acid ether type derivatives, of which there areseveral, are very stable. i'hey are:

may of these is very effective.

There are many derivatives of glutonic acid,

a few of which are shown below:

ax-orr-coon Hr-COOH cm-coon RX- H Hz-COOH BX-CH-COOH RX- H CH-COOHnx-on-coon H nx-erbcoon From the above it can be readily seen what formsthe dicarboxylic acid ethers may take, in which acids the carboxylradicals are separated by four and more carbon atoms.

Where X stands for sulfur, two sulfur atoms may form the linkage. Inother words, compounds of the following types are included in thisinvention:

R s s-cn-c on rr-coon R s SCH-C oon R s s-cn-oo on As may be noted,there are two general groups of dicarboxylic acids among those listedabove, those containing a single ether type radical and those containingtwo ether type radicals. Under many circumstances, the acids containingtwo ether type radicals are preferred because they have -the ability ofgiving material corrosion protection in stagnant salt water. A form ofcorrosion which is probably most difficult to inhibit is that caused bya drop of salt water resting' undisturbed on a metal surface. Few, ifany, corrosion inhibitors which are not of the soap type are capable ofeffectively preventing this corrosion. However, the bis-ether type acidsand particularly the his sulfides of this invention have been proven toprevent corrosion against stagnant salt water for several days.

The compounds of this invention are quite soluble in many organicsolvents. Wherever possible, true solutions are employed in preferenceto colloidal solutions for two reasons: first, because colloids tend tocause emulsiflcation of oleaginous substances with water; and second,colloids may precipitate, in which case at least a portion of the activeingredients would be lost.

The manufacture of most of the compounds of this invention is quitesimple. For example, fumaric acid or maleic acid anhydride may bebrominated and the resulting dibrom succinic acid is then reacted withan alcoholate, alkyl phenolate, mercaptide, selenide, telluride, etc.,having a hydrocarbon radical of sumcient number of carbon atoms toinsure that the reaction product has the required minimum of 16 carbonatoms. This hydrocarbon radical may be normal and/or cyclic, examplesbeing heptyl, methyl cyclohexyl, normal or branched octyl, dimethylcyiclohexyl, ethyl cyclohexyl, nonyl, decyl, undecyl, dodecyl, lauryl,myristyl, cetyl, stearyl, oleyl, arachyl, benzyl, methyl phenyl, ethylphenyl, dimethyl phenyl, propyl phenyl, butyl phenyl, octyl phenyl,naphthyl, alkyl naphthyl, tetrahydronaphthyl, C10 and higherdialicyclic', etc.

The vehicles to which dicarboxylic acids of this invention may be addedfor the purpose of producing corrosion-protective compositions may bedivided into several groups. In the first place, they may be liquids orplastics, the only requirements as to their physical state being (inaddition to their being able to act as carrier for the acids undernormal atmospheric conditions) that they be spreadable over metalsurfaces. Spreading may be accomplished by immersing, flooding,spraying, brushing, trowelling, etc.

After being applied, all or part of the vehicle may be evaporated, or itmay be more or less permanent. In other words, both volatile carriersmay be used, or substances which do not materially volatilize undernormal atmospheric conditions. As to chemical requirements, the vehiclemust be stable under ordinary conditions of storage and use and be inertto the active inhibitors.

Thus the vehicle should referably be substantially neutral, although itmay be weakly acidic or basic, preferably having dissociation constantsnot above about 10 In vehicles of low dielectric constant, ashydrocarbon oils, which are not conducive to ionization of dissolvedelectrolytes. relatively small amounts, 1. e., about .l%-5% of variouscarboxylic acids, such as fatty or naphthenic acids, may be present, andin many instances this may even be beneficial.

Both polar and non-polar vehicles may be employed. .Among the former arewater, alcohols, such as methyl, ethyl, propyl, isopropyl, butyl, amyl,hexyl, cyclohexyl, heptyl, methyl cyclohexyl, octyl, decyl, lauryl,myristyl, cetyl, stearyl, benzyl, etc., alcohols; polyhydric alcohols asethylene glycol, propylene glycol, butylene glycol, glycerol, methylglycerol, etc.; phenol and various alkyl phenols; ketones as acetone,methyl ethyl ketone, diethyl ketone, methyl propyl, methyl butyl,dipropyl ketones, cyclohexanone and higher ketones; keto alcohols asbenzoin, ethers as diethyl ether, disisopropyl ether, diethylenedioxide, beta-beta dichlor diethyl ether, diphenyl oxide, chlorinateddiphenyl oxide, diethylene glycol, triethylene glycol, ethylene glycolmonomenthyl ether, corresponding ethyl, propyl, butyl others; neutralesters of carboxylic and other acids as ethyl. propyl, butyl,

amyl, phenyl, cresyl and higher acetates, propionates, butyrates,lactates, laurates, myristates, palmitates, stearates, oleates,ricinoleates, phthalates, phosphates, phosphites, thio-phosphates,carbonates; natural waxes as carnauba wax, candelilla wax, Japan wax,jojoba oil, sperm oil; fats as tallow, lard oil, olive oil, cottonseedoil, Perilla oil, linseed oil, tung oil, soya bean oil, fiaxseed oil,etc.; weakibases as pyridine, alkyl pyridines,'quinolines, petroleumbases, etc.

Vehicles of little or no polarity comprise hydrocarbons, hydrocarbons asliquid butanes, pentanes, hexanes, heptanes, octanes, benzene, toluene,xylenes, cumene, indene, hydrindene, alkyl naphthalenes; gasolinedistillates, kerosene, gas oil, lubricating oils (which may besoapthickened to form greases), petrolatum, paraffin wax, albinoasphalt, etc.

The amounts of the dicarboxylic acids which must be incorporated in theabove vehiclesto produce corrosion-protective compositions varyconsiderably with the type of vehicle used. As a general rule, thepresence of resinous materials, particularly those of a colloidalnature, calls for relatively larger amounts of inhibitors. Resinousmaterials which interfere with the activity of the inhibitors compriseasphaltenes, petroleum resins, various other natural resins, as rosin,resins formed .by polymerization of drying fatty oils,

phenolformaldehyde resins, glyptal type resinsformed by esterificationof polyhydric alcohols with polycarboxylic acids, etc.

In the absence of such resinous materials,

amounts required of the dicarboxylic acids vary from about .001%uptoabout .1%, although larger amounts may be used. However, where theacids are in colloidal dispersion, rather than in true solution, aconcentration in excess of about .1% may result in relatively quick loss,of part of the inhibitor by precipitation and settling.

In the presence of resins and other colloids, amounts in excess of .1%and up to 5% may be a required. Inasmuch as resins may act as protectivecolloids, compositions containing these large amounts of colloidallydispersed inhibitors, together with resin, may be quite resistant toprecipitation and settling.

Since resinous and gummy substances in the vehicles do call for greateramounts of inhibitors, it is usually desirable to refine normally liquidvehicles thoroughly and free them from gummy substances, therebyimparting to them maximum inhibitor susceptibility. This is ofparticular importance, for example, in lubricating oils, specificallysteam turbine oils, which are advantageously highly refined before theinhibitor is introduced; Suitable refining treatments include, forexample, extraction with selective solvent for aromatic hydrocarbons asliquid S02, phenol, furfural, nitrobenzene, aniline, betabeta-dichlorodiethyl ether, antimony trichloride, etc.; treatment with AlCls,sulfuric acid, clay, etc.; as the treatment produces a sludge, specialcare must be taken to remove itvery thoroughly and completely.

Applications of the various corrosion-protective compositions vary overa wide range. Hydrocarbon compositions are of special importance. Forexample, gasolines stored in drums may cause rusting of the drumsbecause of the accumulation of water. This is particularly bad intropical countries where the moisture content of the air is high, andwide variations in temperature over a 24-hour cycle cause considerablebreathing of the drums.

cellent protection in all of the above instances.

Rusting of ferrous metals exposed to the atmosphere during usage orstorage is a serious problem. This is of particular importance whereaccurately machined parts must be preserved. Slushing oils comprisingvarious types of liquid or plastic hydrocarbons, fats, waxes, lanolins,are employed to protect the metals against this attack, and theinhibitors of this invention have great value as an active component insuch slushing oils.

Internal corrosion of ferrous metal pipe lines which transporthydrocarbons has been a matter of much concern, and the presence ofsmall amounts of the dicarboxylic 'acids of this invention (especiallythose having two ether-type radicals) in hydrocarbon oils, particularlyrefined light hydrocarbon oils such as gasoline, greatly retards orfully prevents pipe line corrosion.

Cutting oils, EP lubricants, due to their content of sulfur and/orchlorine in various active forms, frequently are quite corrosive. Thediscarboxylic acids eifectively inhibit this corrosion.

Among the non-hydrocarbon compositions which frequently cause corrosiondifliculties, anti-freezes used in automobile radiators and the like maybe mentioned. The dicarboxylic acids effectively eliminate theircorrosiveness. Anti-freezes usually comprise or consist of watermisciblealcohols, such as methanol, ethanol, isopropanol, glycol, glycerol, etc.

So-called hydraulic oils, damping oils, etc.,

which frequently are based on non-hydrocarbon liquids, such as variousalcohols, esters, etc., have in the past introduced some corrosiondifliculties which can effectively be prevented by the acids of thisinvention.

Dispersions of the dicarboxylic di-fatty acids in water may be useful inthe rust-proofing of metals which after treatment must not be greasy as,for example, various machine parts in the textile industries,particularly in the knitting of fine dry goods. If desired, solutions ordispersions in low-boiling alcohols, etc., may beused for the samepurpose.

It is understood that the corrosion-protective compositions of thisinvention may contain other ingredients in addition to the vehicle andthe dicarboxylic acids. However, such additional ingredients must bechemically inert to the acid and the vehicle employed. Thus strongoxidizing agents as chlorine, peroxides, etc., must be avoided as theytend to destroy the inhibitors. Strong bases, particularly in ionizingvehicles. as in water, alcohols, etc., will neutralize the di-acids andExamples The effectiveness of dicarboxylic acids of this invention insuppressing corrosion was determined by a modified testflwherein apolished steel strip was subjected to the action of a vigorously stirredemulsion of a turbo raflinate having S. U. viscosity at 100 F. of 150seconds with by volume sea Water at 167 F. Below are some typicalresults:

Additive Water Time Corrosion Hours .01% alpha beta Synthetic sea 48Noneperfect dilauric dith io water. protection. succinic acid Distill eat 48 P r ct Mono thio lauryl e w e succinic gen {8 yvigttell etic sea16 Partly corroded.

1 After the test was completed, stirring was discontinued and the steelstrip was allowed to drop into the sea water at the bottom of thecontainer, remaining there undisturbed for four days. At the end of thisperiod, only a few small rust spots had developed.

We claim as our invention:

1. A corrosion-preventive composition comprising predominantly a stable,substantially neutral and chlorine free vehicle containing finelydispersed a small corrosion inhibiting amount of a free dicarboxylicacid having at least 16 carbon atoms and possessing at least oneether-type radical of an element selected from the group consisting ofO, S, Se and Te, which ether-type radiing predominantly a stable,substantially neutral and chlorine-free vehicle containing finelydispersed a small corrosion inhibiting amount of a succinic acid etherhaving at least 16 carbon atoms, which ether radical branches from thecarbon chain linking the carboxyl radicals.

10. A corrosion-preventive composition comprising predominantly astable, substantially neu- 1y dispersed a corrosion-inhibiting amount ofa cal branches from the carbon chain linking the carboxyl radical.

2. The composition of claim 1 wherein the number of carbon atoms in saidacid is between 20 and 60.

3. The composition of claim 1 wherein said vehicle has a dissociationconstant below 10-.

4. The composition of claim 1 wherein said acid is in'truesolution.

5. The composition of claim 1 wherein said acid is in colloidal.solution.

6. A corrosion-preventive composition comprising predominantly a stable,substantially neutral hydrocarbon vehicle containing finely dispersed asmall corrosion inhibiting amount of a free dicarboxylic acid having atleast 16 carbon, atoms and having the formula coon ((R-X(cH,).) t-(wherein u is an integer of 1 up to about 8, v is an integer of from 0 toabout 8, w is at least 1 and not greater than u, X is an elementselected from the group consisting of O, S, Se and Te, and R is ahydrocarbon radical, and the unoccupied valences are tied to hydrogen orhydrocarbon radicals.

7. The composition of claim 6 where u and w are 2 and v is 0.

8. The composition of claim 6 wherein said vehicle comprises mineraloil.

9. A corrosion-preventive composition compris succinic acid disulfidehaving at least 16 carbon atoms.

12. A corrosion-preventive composition comprising predominantly astable, substantially neutral chlorine-free vehicle containing finelydispersed a small corrosion inhibiting amount of a free dicarboxylicacid having at least 16 carbon atoms and having the formula wherein X isan element selected from the group consisting of O, S, Se and Te, and Ris a hydrocarbon radical.

13. A corrosion-preventive composition comprising predominantly a.substantially neutral oleaginous substance containing a small corrosioninhibiting amount of a free dicarboxylic acid having at least 16 carbonatoms and possessing at least one ether-type radical of an elementselected from the group consisting of O, S, Se and Te, which ether-typeradical branches from the carbon chain linking the carboxyl radicals.

14. The composition of claim 13 in which said substance is normallyliquid.

15. The composition of claim 13 in which said substance is normallyplastic.

16. A corrosion-preventive composition comprising predominantly asubstantially neutral oleaginous substance free from resins containingfinely dispersed .001 %.1% of a free dicarboxylic acid having at least16 carbon atoms, and possessing at least one ether-type radical of anelement selected from the group consisting of O, S, Se and Te, whichether-type radical branches from the carbon chain linking the carboxylradicals.

17. A corrosion-preventive composition comprising predominantly asubstantially neutral oleaginous substance containing resins and finelydispersed .1 %-5% of a free dicarboxylic acid having at least 16 carbonatoms and possessing at lease one ether-type radical of an elementselected from the group consisting of O, S, Se and Te, which ether-typeradical branches from the carbon chain linking the carboxyl radicals.

18. A corrosion-preventive lubricating oil containing finely dispersed.001%-.1% of a free dicarboxylic acid having at least 16 carbon atomsand possessing at least one ether-type radical of an element selectedfrom the group consisting of O, S, Se and Te, which ether-type radicalbranches from the carbon chain linking the carboxyl radicals.

19. A corrosion-preventive composition comprising predominantly acarboxylic acid ester containing finely dispersed a small corrosioninhibiting amount of a tree dicarboxylic acid having at least 16 carbonatoms and possessing at least one ether-type radical of an elementselected from the group consisting of O, S, Se and Te, which ether-typeradical branches from the carbon chain linking the carboxyl radicals.

20. A corrosion-preventive composition comprising predominantly a fat,and finely dispersed therein a small corrosion inhibiting amount of afree dicarboxylic acid having at least 16 carbon atoms and possessing atleast one ether-type radical of an element selected from the groupconsisting of O, S, Se and Te, which ether-type radical branches fromthecarbon chain linking the carboxyl radicals.

21. A non-corrosive anti-freeze composition comprising predominantly awater-soluble alcohol and finely dispersed therein a small corrosioninhibiting amount of a free dicarboxylic acid having at least 16 carbonatoms and possessing at least one ether-type radical of an elementselected from the group consisting of O, S, Se and Te, which ether-typeradical branches from the carbon chain linking the carboxyl radicals.

22. The process of inhibiting internal corrosion in a ferrous metal pipeline carrying refined light hydrocarbon oil comprising passing throughthe pipe line said liquid hydrocarbon containing between .001% and .1%of a free dicarboxylic acid having at least 16 carbon atoms andpossessing at least one ether-type radical of an element selected fromthe group consisting 01 O, S, Se and Te, which ether-type radicalbranches from the carbon chain linking the carboxyl radicals.

23. A corrosion-preventive composition comprising predominantly astable, substantially neutral and chlorine-free vehicle containingfinely dispersed a corrosion-inhibiting amount of a free dicarboxylicacid having at least 16 carbon atoms. and having the formula wherein Xis an element selected-from the group consisting of O, S, Se and Te andR is a hydrocarbon radical.

24. A corrosion-preventive composition comprising predominantly astable, substantially neutral vehicle containing finely dispersed asmall corrosion inhibiting amount of a tree dicarboxylic acid having atleast 16 carbon atoms and having the formula n-x-on-coon Hi-COOH whereinX is an element selected from the group consisting of O, S, Se and Teand R is a hydrocarbon radical.

EMME'I'I. R. BARNUM. ERNEST W. ZUBLIN.

Certificate of Correction Patent No. 2,371,142.

March 13, 1945'.

EMMETT R. BARNUM ET AL.

It is hereby certified that-error appears in the printed specificationof the above numbered patent reqmring correction as follows: Page 1,second column, lines 13 to 18 inclusive, strike out the formula andinsert instead the followingand that the said Letters Patent should beread with this correction th th t t same may conform to the record ofthe case in the Patent Office. 6mm a he Signed and sealed this 3rd dayof July, A. D. 1945.

[SEAL] LESLIE FRAZER, Acting Uommissioner of Patents.

